Oregon ZooOregon spotted frogs are a candidate for protection under the Endangered Species Act.

The Oregon spotted frog may hop onto the federal endangered species list. The U.S. Fish & Wildlife Service is evaluating the frog's status as part of a 2011 court settlement that required the agency to step up its review of 757 plant and animal species.

As part of the work, the agency is asking the public to report sightings of the frog and information about its habitat. The information should be directed by April 20 to wildlife biologist Deanna Lynch at the service's Division of Listing and Recovery in Lacey, Wash.

The frog is named for the black spots on its head, back, sides and legs. Juveniles are usually brown or olive green on the back, with white or cream-colored abdomen and underlegs. Adults are brown to red on the back, becoming redder as they age, according to the fish and wildlife service.

The agency describes them as the most aquatic native frog in the Pacific Northwest, almost always found in or near a perennial body of water that has shallow zones and abundant plants that is uses for basking or cover.

The spotted frog, which lives in wetlands from southwestern British Columbia to Oregon's Klamath Valley, has been a candidate for listing as threatened or endangered since 1993. The wildlife service has monitored frog populations since then but said further action was precluded by other work.

The environmental group Center for Biological Diversity filed suit to force the agency to take action. An agreement signed last summer gives the service until 2018 to decide whether multiple plants and animals deserve full listing under the Endangered Species Act. More than 250, like the frog, are already candidates for listing.

About 60 Northwest species are among the plants and animals affected by the court settlement, including the Oregon spotted frog, the Seattle area's Lake Sammamish kokanee and 32 types of slugs and snails.

Noah Greenwald, endangered species program director with the Center, said spotted frogs have disappeared from most of their former range and are found now in only 50 sites. Habitat loss, especially of wetlands adjacent to rivers and streams, is a key factor in their decline, he said.

Other factors include contamination and the introduction of predators such as bullfrogs.

"The Oregon spotted frog badly needs the help that only the Endangered Species Act can give it, so we're glad to see that it's one step closer," Greenwald said in a news release.